Throttle control and failure accommodation

ABSTRACT

One embodiment of the present invention is an apparatus including an internal combustion engine for powering a ground travelling vehicle, a throttle control arrangement including a device for sensing position of an operator-adjustable pedal to provide a throttle control signal, a first sensor to sense rotational speed of the engine, a second sensor to sense brake status of the vehicle, a way to determine failure of the throttle control signal, and a way to operate the engine in a limp-home mode in response to the failure, which includes fueling the engine during the limp-home mode of operation in accordance with idle position of the pedal, rotational speed of the engine, and the brake status.

RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication No. 60/399,001 filed Jul. 27, 2002, and entitled THROTTLECONTROL AND FAILURE ACCOMMODATION. The provisional patent application isincorporated herein by reference.

BACKGROUND

The present invention relates to internal combustion engines, and moreparticularly, but not exclusively, is directed to sensor signalprocessing for throttle control of an engine.

With the advent of electronic control systems, sensors are frequentlyused to receive input of various parameters. When a sensor fails, it isalso frequently desirable to adjust the control system to accommodatefor this failure in some manner. More particularly, there is an interestin sensing position of operator-adjustable controls, such as a throttleinput, and accommodating failures of corresponding sensors. Thus, anongoing need exists for further contributions in this area oftechnology.

SUMMARY

One embodiment of the present invention is a unique technique forcontrolling an internal combustion engine. Other embodiments includeunique methods, systems, apparatus, and devices for processing sensorsignals relating to throttle control of an engine.

Yet other embodiments include unique methods, systems, and apparatus toaccommodate a throttle control failure. In one form, a unique limp-homemode of engine operation is provided through the failure accommodation.

Still other embodiments include unique throttle control sensing methods,systems, and apparatus. These embodiments are directed to throttlecontrol arrangement with two or more sensors each operable to detect arange of nonidle throttle control positions.

A further embodiment includes an internal combustion engine; a throttlecontrol arrangement including an operator adjustable pedal and a set ofsensors each operable to sense at least a portion of a range of multiplenonidle positions of the pedal; and a controller responsive to thethrottle control arrangement to generate one or more throttle signals.In one form, the controller includes operating logic to do one or moreof the following: detect an out-of-range condition of one or more of thesensors, detect a conformance error of one sensor relative to another,determine throttle idle status form the sensors, determine one or moreparameters to calibrate the sensor outputs, accounting for manufacturingvariation and/or sensor drift.

Yet a further embodiment includes: operating an internal combustionengine fueled in accordance with an operator-adjusted throttle control;registering at least a portion of a range of multiple nonidle positionsof the operator-adjusted throttle control with each of two or moresensors; detecting an out-of-range condition of one or more of thesensors; determining an error based on a difference in output between atleast two of the sensors; determining idle status from the sensors;and/or adjusting the sensor outputs to account for sensor drift and/oran expected range of manufacturing variation.

Another embodiment includes operating an internal combustion engine inresponse to a throttle signal provided with an operator-adjustedthrottle control; generating an idle status signal corresponding to anidle position of this control; detecting a failure; and adjusting fuelprovided to the engine as a function of the idle status signal. In oneform, this adjustment may further be determined as a function ofrotational engine speed and braking status of a vehicle powered by theengine.

Still another embodiment includes moving a ground-traveling vehicle withan internal combustion engine in response to a first operator-adjustedfueling control; detecting a failure of this control; adjustingoperation of the engine in response to it to limit vehicle speed afterthe failure; and operating the engine after the failure in response to asecond operator-adjusted fueling control to selectively move the vehicleat a greater speed than permitted with the first operator-adjusted fuelcontrol.

Yet another embodiment includes a ground-traveling vehicle; an internalcombustion engine operable to power motion of the vehicle; a throttlecontrol responsive to an operator of the vehicle; a cruise controlresponsive to the operator of the vehicle; a vehicle speed sensor; and acontroller. This controller responds to the throttle control to regulatefueling of the engine and is operable to detect a throttle controlfailure and regulate engine operation with the throttle control in anaccommodation mode in response to the failure. The controller isresponsive to operator input with the cruise control and the vehiclespeed sensor to permit the engine to power the vehicle at a vehiclespeed greater than with the throttle control during engine operation inthe accommodation mode.

A further embodiment includes operating a vehicle including an internalcombustion engine fueled in accordance with an operator-adjusted fuelingcontrol; registering at least a portion of a range of multiple nonidlepositions of the operator-adjusted throttle control with each of two ormore sensors; detecting a failure of one of the sensors; determiningidle status of the throttle control after the failure; and fueling theengine based on a limp-home mode of operation in accordance with theidle status.

Another embodiment includes an internal combustion engine; a throttlecontrol arrangement, including an operator-adjustable pedal and a set ofsensors to redundantly sense at least a portion of a range of multiplenonidle positions of the pedal; and a controller responsive to the setof sensors to determine an engine fueling signal corresponding to theposition of the pedal and an idle status signal representative of idleposition status of the pedal. The controller is operable to detectfailure of the throttle control arrangement and control the engine in afailure accommodation mode. The controller generates the engine fuelingsignal as a function of the idle status signal during the failureaccommodation mode.

Accordingly, it is one object of the present invention to provide aunique technique for controlling an internal combustion engine.

Another object of the present invention is to provide a unique method,system, apparatus, or device for processing sensor signals relating tothrottle control of an engine.

Further embodiments, forms, features, objects, advantages, benefits, andaspects of the present invention shall become apparent from the detaileddescription and drawings provided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a vehicle and engine system.

FIGS. 2–4 are flowcharts illustrating a limp-home mode of operation ofthe system of FIG. 1 to accommodate a throttle-related failure.

FIG. 5 is a graph of fueling versus engine speed relating to the mode ofoperation of FIG. 2.

FIG. 6 is a diagrammatic view of one form of a throttle controlarrangement to provide the throttle control in the system of FIG. 1.

FIG. 7 is a diagrammatic view of an alternative form of a throttlecontrol arrangement to provide the throttle control in the system ofFIG. 1.

FIGS. 8–11 are control logic diagrams illustrating various operationsinvolving the throttle control arrangement of FIG. 7.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described embodiments, and any further applications of theprinciples of the invention as described herein are contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

FIG. 1 depicts vehicle 20 of one embodiment of the present invention. Asdepicted, vehicle 20 includes wheels 21 to travel along the ground, andmay be of any type, such as a pick-up truck, a heavy duty truck, apassenger car or van, or an off-road variety to name just a few. Vehicle20 includes engine 30 with a number of cylinders C1–C6 each having acorresponding reciprocating piston P1–P6 that is rotatably coupled tocrankshaft 34 in a conventional manner. Each cylinder/piston paircorresponds to a combustion chamber configured to receive a combustibleair/fuel charge. Engine 30 is of a four cycle type with noncontinuouscombustion in each cylinder C1–C6 intermittently contributing power inaccordance with a timed sequence of fueling and ignition operations. Inlieu of a reciprocating piston-based engine, a rotor-based engine may beutilized in an alternative embodiment of the present invention. Engine30 is configured to operate with a diesel fuel supplied from fuel sourcethat is injected with injectors, (now shown), and is correspondingly ofthe Compression Ignition (CI) variety. In one application, engine 30 isa diesel-fueled, in-line six cylinder engine utilized with a light dutytruck form of vehicle 20; however, other embodiments may have more orfewer cylinders in any geometric arrangement; may operate over adifferent number of cycles, such as a two cycle type; may have differentfueling and/or may be of a different vehicle type, to name only a fewpossible variations. In a further example, engine 30 could be configuredfor other fuel types as an alternative or in addition to diesel such asgasoline, alcohol, a gaseous fuel (a “gaseous fuel” refers to a fuelwhich is in the gaseous state when contained at standard temperature andpressure), a combination of these, or a different fuel as would occur tothose skilled in the art. Correspondingly, engine 30 can be of adifferent ignition type, such as a Spark Ignition (SI) variety.

Crankshaft 34 is connected to a transmission and other drive trainmembers 80 in a conventional manner. The transmission may be of anautomatic, manual, semi-manual, or different type as would occur tothose skilled in the art. Transmission and other drive train members 80operate to move vehicle 20 with mechanical power provided by crankshaft34.

Engine 20 also includes fueling subsystem 40. Subsystem 40 includes afuel source operatively coupled to a fueling conduit that is in fluidcommunication with a fuel rail to selectively supply fuel to theinjectors (not shown) associated with each cylinder C1–C6. Fueling withinjectors may be by port injection, direct injection, or using suchother injection techniques as would occur to those skilled in the art.In other embodiments, fueling may be provided in a different manner withor without injectors as appropriate to the arrangement.

Air is supplied to cylinders C1–C6 via air handling subsystem 50. Airhandling subsystem 50 includes a throttle valve positioned therealong tocontrol air flow through a conduit to an intake manifold. Air from theintake manifold is mixed with fuel from the injectors to selectivelyprovide a combustible charge in each of cylinders C1–C6. Engine 30 alsoincludes exhaust subsystem 70. Exhaust from engine 30 exits alongexhaust subsystem 70 through a conduit in a standard manner.

The air handling subsystem 50 and exhaust system 70 may includecomponents of a turbocharger (not shown) including a compressor whichdraws air through an inlet into a conduit of subsystem 50. Subsystem 50may further include an aftercooler to cool air compressed by thiscompressor. For a turbocharger embodiment, exhaust subsystem 70 caninclude a turbine powered by the exhaust stream to drive the compressor,and further may have a wastegate to selectively by-pass exhaust awayfrom the turbine.

Vehicle 20 further includes controller 90 operatively coupled to airhandling subsystem 50, fueling subsystem 40, exhaust subsystem 70, andoperator fueling controls 100. Fueling controls 100 directly orindirectly change the amount of fuel provided to engine 30 in responseto movement by an operator. Included in fueling controls 100 are cruisecontrol 102 and throttle control 110. Throttle control 110 may be any ofa variety of different types including, but not limited to, one of thethrottle control arrangements described in connection with FIG. 6 orFIG. 7 hereinafter. Similarly, cruise control 102 may be any of avariety of operator-manipulated devices to set and/or adjust speed of avehicle—typically in a cruising speed range.

Controller 90 is also coupled to rotation sensor 91 which is configuredto supply signal R indicative of rotation of crankshaft 34. Preferably,signal R provides conventional crank angle information about engine 30which may be utilized for timing operation of engine 30. Rotationalengine speed, designated as signal n, is determined from signal R in aconventional manner. In one embodiment, signal R corresponds to a pulsetrain, the frequency of which is directly proportional to the rotationalspeed of engine 30. Signal n may then be provided by monitoring thepulse train frequency. U.S. Pat. No. 5,165,271 to Stepper et al.; U.S.Pat. No. 5,460,134 to Ott et al.; and U.S. Pat. No. 5,469,823 to Ott etal. are representative of an arrangement suitable for providing signalsR and n. In other embodiments, signal n may be determined directly froma rotational speed sensing arrangement or in a different manner.

Controller 90 is further operatively coupled to vehicle brake sensor 92and vehicle speed sensor 94. Vehicle brake sensor 92 provides signalinformation that can be used to determine whether a vehicle brake isbeing applied. Vehicle speed sensor 94 provides signal information thatcan be used to determine the speed of vehicle 20. Sensors 91, 92, 94 canbe any of a number of sensors and/or sensing subsystems known in theart, and may provide a signal in either a digital or analog formatcompatible with associated equipment. Correspondingly, equipment coupledto each sensor is configured to condition and convert sensor signals tothe appropriate format, as required. Additionally, controller 90 may beoperatively coupled to a number of other devices and/or subsystems ofvehicle 20 and/or engine 30; for example: a temperature sensor toprovide engine temperature signal information, a pressure sensor toprovide intake manifold pressure signal information, an exhaust gasoxygen sensor, an electrical power generation subsystem, and/or operatorcompartment subsystem(s), to name just a few.

Controller 90 may be comprised of digital circuitry; analog circuitry;optical devices; pneumatic, hydraulic, or other mechanical devices, or acombination of these. Also, controller 90 may be programmable, adedicated state machine, or a hybrid combination of programmable anddedicated hardware. Controller 90 can be an electronic circuit comprisedof one or more components that are assembled as a common unit.Alternatively, for a multiple component embodiment, one or more of thesecomponents may be distributed throughout the relevant system. Controller90 operates in accordance with operating logic to implement variousaspects of the inventions described hereinafter in connection with FIGS.2–11. This operating logic may be hardwired and/or provided byprogramming. In one embodiment, controller 90 includes an integratedprocessing unit operatively coupled to one or more solid-state memorydevices that at least partially include the operating logic in the formof program instructions executed by the processing unit. In thisembodiment, the controller and supporting components are provided in acommon unit in the form of an Engine Control Module (ECM). Memory forthis embodiment may be either volatile or nonvolatile and mayadditionally or alternatively be of the magnetic, optical, or such othervariety as would occur to one skilled in the art. Besides the memory andprocessing unit, controller 90 can include any control clocks,interfaces, signal conditioners, filters, Analog-to-Digital (A/D)converters, Digital-to-Analog (D/A) converters, communication ports, orother types of operators as would occur to those skilled in the art toimplement the principles of the present invention.

FIG. 2 is a flow chart of an embodiment of a limp-home routine 120 forvehicle 20 that may be executed in accordance with the operating logicof controller 90. Routine 120 facilitates operation of vehicle 20 toaccommodate a throttle control failure such that a desired destinationcan be reached prior to repairing the failure. Such destinations couldinclude a repair garage, one's home, a service station, etc. Routine 120begins with conditional 122 that tests whether a throttle controlfailure condition exists. If the result of conditional 122 is negative,routine 120 loops back to conditional 122 unless it has an affirmativeresult. For an affirmative result of conditional 122, routine 120proceeds to operation 124. Operation 124 assigns the current fuelingvalue of engine 30 to the variable Limp-Home Fueling Amount (LHFA). Fromoperation 124, routine 120 proceeds to subroutine 130 to determineLimp-Home Maximum Fueling (LHMF) as described below.

FIG. 3 is a flowchart describing the operation of subroutine 130 that isused to determine the value of LHMF. Routine 130 begins at operation 132in which Filtered Engine Speed (FES) is determined. FES is provided by afirst order digital filter, being determined as a function of a filterconstant and engine speed n. Engine speed n may be obtained, forexample, using signal information communicated from sensor 91 tocontroller 90. From operation 132, routine 130 proceeds to operation 134which sets the value of LHMF in accordance with the graph shown in FIG.5.

FIG. 5 is a graph showing percent fueling on its vertical axis andengine speed on its horizontal axis. It defines a number of operatingregions R1, R2, R3 and R4. A number of fueling values are indicated onthe vertical axis: fueling offset, break maximum fueling (BMF), minimumfueling, and idle fueling. The LHMF value is selected from a fuelingcurve, comprised of two line segments: the fueling slope segment and thegenerally horizontal line segment labeled LMF (Lowest Maximum Fueling).These two line segments form the upper boundary of operating regions R1,R2 and R3 of the FIG. 5 graph. Idle speed at the left-most extreme ofregions on R1 and R4, and absolute maximum engine speed (ABS. MAX.) atthe right most extreme region of R3 are found along the horizontal axis.Additionally, regions R1–R4 are shown within a 100% fueling curve thatcorresponds to nominal fueling limits of engine 30.

Returning to operation 134 of subroutine 130, the criteria for settingLHMF can be understood with reference to the graph of FIG. 5. If FES isof a value that places it in the fueling slope segment of FIG. 5, LHMFis set equal to Fueling Offset—(Limp-Home Fueling Slope*FES). Otherwise,LHMF is set to the Lowest Maximum Fueling (LMF) value, corresponding tothe generally horizontal upper boundary of regions R2 and R3 of FIG. 5.

From operation 134, subroutine 130 proceeds to conditional 136 whichtests whether the condition “Brake On” is true. Condition “Brake On” maybe determined from signal information communicated from vehicle brakesensor 92 to controller 90. If conditional 136 is negative, routine 130returns to routine 120. If conditional 136 is affirmative, routine 130proceeds to operation 138 which sets the value of LHMF equal to BMF.This can be understood with reference to the graph of FIG. 5, whichshows threshold BMF defining an upper boundary or limit for fueling inregion R4. As a result, the maximum fueling during vehicle braking (BMF)is lower than LHMF. From operation 138, subroutine 130 returns toroutine 120.

Returning to FIG. 2, routine 120 proceeds from subroutine 130 toconditional 142 which tests whether the value of Limp-Home FuelingAmount (LHFA), as preset in operation 124, is greater than the value ofLHMF. If conditional 142 is negative, routine 120 proceeds to subroutine150 which is described below. If conditional 142 is affirmative, routine120 proceeds to operation 144. Operation 144 limits the value of LHFA tothe value of LHMF. From operation 144, routine 120 enters subroutine150, which determines subsequent limp-home fueling operations that aredescribed as follows.

FIG. 4 is a flowchart describing the operation of subroutine 150 whichbegins with execution of subroutine 130 as was previously described inconnection with FIG. 3. From subroutine 130, subroutine 150 proceeds toconditional 152 which tests whether the value of FES is greater than thevalue of a Limp Home Vehicle Engine Speed Limit (LHSL). If conditional152 is negative, subroutine 150 proceeds to conditional 158 which isdescribed below. If conditional 152 is affirmative, subroutine 150proceeds to conditional 154 which tests whether the vehicle speed (VS)is greater than a Limp-Home Speed Threshold (LHST). VS may be determinedfrom signal information communicated from vehicle speed sensor 94 tocontroller 90. If conditional 154 is negative, subroutine 150 proceedsto conditional 158 (described below). If conditional 154 is affirmative,subroutine 150 proceeds to operation 156.

Operation 156 regulates engine 30 in accordance with a limp-home enginespeed governor in relation to regions R1, R2 and R4 shown in the graphof FIG. 5. If engine speed is determined to be in region R3 (arelatively high value), while vehicle speed is determined to be low,this governing relationship is not implemented, as might occur when thevehicle is in a low gear. Conversely, when VS is sufficiently high,speed governing results which provides an engine speed limit, and inconjunction with LHMF, limits vehicle speed to a level below what istypically permitted when the limp-home mode is not implemented. Becausethis governor only operates above a certain speed, it can be referred toas high speed governor (HSG). Referring to FIG. 5, there are two enginespeed limiting lines for the governor, HSG1 and HSG2. HSG1 is themaximum engine speed line for the governor relative to fueling when“Brake On” is true. As a result, it should be understood that it forms acorner with the horizontal line corresponding to BMF. HSG2 is themaximum speed line for the governor relative to fueling when “Brake On”is false. HSG2 forms a corner with LMF. Operation along lines HSG1 andHSG2 subject to the respective fueling levels BMF and LMF serves tolimit vehicle speed VS during the limp-home mode of operation inresponse to throttle control 110 compared to vehicle speed permittedduring nominal operation. From operation 156, subroutine 150 proceeds toconditional 158.

Conditional 158 tests whether the value of Limp-Home Fueling Limit(LHFL) is greater than (LHMF+Maximum Fuel Ramp Rate (MRR)). Ifconditional 158 is negative, subroutine 150 proceeds to operation 162which sets the value of LHFL equal to the value of LHMF (LHFL=LHMF). Ifconditional 158 is affirmative, subroutine 150 proceeds to operation 160to decrease LHFL by MRR (LHFL=LHFL−MRR). From either operation 162 oroperation 160, subroutine 150 proceeds to conditional 164.

Conditional 164 tests whether throttle control 110 is at an idleposition. If conditional 164 is negative, subroutine 150 proceeds toconditional 168 (described below). If conditional 164 is affirmative,subroutine 150 proceeds to operation 166 which sets the fueling level atan idle fueling level as shown in connection with the graph of FIG. 5.Conditional 168 tests whether vehicle 20 was at idle during a priorexecution (last interval) of subroutine 150, which is stored during eachsubroutine 150 execution.

If conditional 168 is negative, subroutine 150 proceeds to operation 170which increases LHFA by an incremental value (LHFA=LHFA+INCREMENT). Thisincremental value may be an empirically determined value specific toengine 30 or to a class of engines to which engine 30 belongs and may beprovided as a predefined stored value. If conditional 168 isaffirmative, subroutine 150 proceeds to operation 172 which sets thevalue of LHFA equal an initial fueling level. From operations 172 and170 subroutine 150 proceeds to operation 174, and then returns toroutine 120.

Operation 174 limits LHFA to LHFL. In this manner, operation 174provides a fueling limitation for engine 30. The limited LHFA is used tocontrol engine 30 by communicating appropriate signal information fromcontroller 90 to fueling subsystem 40. Fueling subsystem 40 may then,for example, control fuel injectors to regulate the amount of fuelprovided to cylinders C1–C6.

Returning to FIG. 2, routine 120 proceeds from subroutine 150 toconditional 180 to determine if the failure condition has been removedby a reset action. If the value of conditional 180 is negative, routine120 proceeds to operation 150. If the value of the conditional 180 isaffirmative, routine 120 returns back to conditional 122, correspondingto a removal of the failure condition.

In certain embodiments, an operator may desire to operate vehicle 20 ata road speed greater than permitted with throttle control 110 duringfailure accommodation with subroutine 150. Cruise control 102 can beused as an alternative fueling control 100 to provide greater vehiclespeeds for such embodiments. Typically, vehicle 20 needs to reach aminimum road speed as detected with sensor 92 before cruise control 102is activated. The range of vehicle speeds provided during control ofengine 30 with subroutine 150 in the limp-home mode can be selected toinclude such a minimum road speed when applicable. Accordingly, cruisecontrol 102 can be activated once this minimum is reached to selectivelyincrease vehicle speed to a level greater than permitted through thethrottle control failure accommodation provided by subroutine 150.Nonetheless, in other embodiments, vehicle speed may not besignificantly limited with routine 150, and/or it may be desirable tospeed-limit cruise control 102 or render cruise control 102 inactive. Instill other embodiments, cruise control 102 may be absent.

FIG. 6 is one embodiment of a throttle control arrangement 210 that canbe used as throttle control 110 and correspondingly with routine 120. Anoperator-adjustable pedal 212 is provided that may be positioned by theoperator of vehicle 20 to command a certain throttle level. Arrangement210 further includes position sensor 214 and idle sensor 216. Sensor 214includes a rheostat or potentiometer with a movable member coupled tomove in response to movement of pedal 212. A voltage is applied tosensor 214 to provide a changing output voltage at one of its terminalsthat corresponds to the pedal position. This output voltage is typicallyconverted into a digital form. For implementation with routine 120,controller 90 could use the resulting signal to perform throttleadjustment operations and/or detect a throttle control failure forroutine 120.

Idle sensor 216 can be in the form of a switch or other type of discretesignal indicating device responsive to a change in position of pedal 212from idle. Switch 216 provides a corresponding two-state idle statussignal with one state indicating an idle position of pedal 212 and theother state indicating a nonidle position of pedal 212. Forimplementation with routine 120, idle sensor 216 provides the idlestatus that can be used in the test of conditional 164 for subroutine150.

FIG. 7 depicts throttle control arrangement 220 of another embodimentthat can be used as throttle control 110 and correspondingly withroutine 120. An operator-adjustable pedal 222 is provided that may bepositioned by the operator of vehicle 20 to command a certain throttlelevel. Arrangement 220 further includes dual pedal position sensors 224and 226. Sensors 224 and 226 can each be the same as sensor 214described in connection arrangement 210. Each sensor 224 and 226 has aseparate voltage supply (not shown) to generate a pair of pedal positionsignals S1 and S2, respectively each representative of a range ofdifferent positions of pedal 222. For implementation with routine 120,controller 90 could use signals S1 and S2 to perform throttle adjustmentoperations an/or detect a throttle control failure for routine 120 as isfurther described in connection with FIGS. 8–11 hereinafter.

Sensors 214, 216, 224, and/or 226 may be calibrated and/or filtered withrespect to known values, empirically determined values, and/or otheralgorithms to improve the functioning of throttle control 110. In otherembodiments, sensors 214, 224, and/or 226 can be another type used withor without a rheostat, potentiometer, or other variable resistanceelement, such as: a capacitor or inductor that varies with pedalposition, a device to indicate position based on orientation and/orstrength of a magnetic field, a pedal position indicated in terms ofsensed pressure, and optical position sensing device, a combination ofthese, and/or a different position sensing device as would occur to oneskilled in the art. Additionally or alternatively, sensors that have apredefined number of discrete output levels can be arranged to detectdifferent pedal positions. By way of nonlimiting example, a switch withseveral different positions and corresponding poles can be coupled to aresistive network to provide a different output voltage for each of itspositions. By moving the switch actuator with the pedal, different pedalpositions can represented by the different discrete voltages. Likewise,logic devices could be used with the different poles to generate a rangeof binary values corresponding to different pedal positions. In stillother embodiments, in addition or as an alternative to a pedal, theoperator-adjustable member of the throttle control can be a slider, alever, a rotary dial, and/or a different input device type as wouldoccur to one skilled in the art.

FIGS. 8–11 depict different control logic diagrams associated withvarious operations that can be performed in accordance with theoperating logic of controller 90 when arrangement 220 is used asthrottle control 110. Control logic 245, 260, 300, and 400 of FIGS.8–11, respectively, includes various operators, some of which havetwo-state (binary) inputs and/or outputs and others with inputs and/oroutputs for which there are more than two states possible (>2 discretevalues). Unless otherwise indicated, as used in FIGS. 8–11, ORoperators, AND operators, inverters, debouncer signal inputs andoutputs, latching logic, comparator outputs, conditional operators, andtoggle inputs to logical switches are of the two-state type; and adders,multipliers, comparator inputs, minimum value selectors, absolute valueoperators, throttle range calculators, limiters, debouncer delay inputs,and input poles and outputs of logical switches are not. Referringspecifically to FIG. 8, control logic 245 is depicted. Control logic 245determines if a failure of sensor 224 or 226 has occurred. Logic 124 canbe used to perform the test of conditional 122 in routine 120 toactivate limp-home failure accommodation. Logic 245 includes logical ORoperator 230 with three inputs 232, 234 and 236 and output 238. Input232 indicates the value of signal S1 is out-of-range because its valueis too high, input 234 indicates the value of signal S1 is out-of-rangebecause its value is too low, and input 236 indicates a voltage supplyerror relating to the generation of signal S1 with sensor 224. Theoutput 238 of logical OR operator 230 is true if one or more of theinputs 232, 234, or 236 is true. Output 238 provides two-state signalS1OOR.

Logic 245 also includes logical OR operator 240 with three inputs 242,244 and 246 and output 248. Input 242 indicates the value of signal S2is out-of-range because its value is too high, input 244 indicates thevalue of signal S2 is out-of-range because its value is too low, andinput 246 indicates a voltage supply error relating to the generation ofsignal S2 with sensor 226. The output 248 of logical OR operator 240 istrue if one or more of the inputs 242, 244, or 246 is true. Output 248provides two-state signal S2OOR.

Logic 245 further includes logical OR operator 250 with output 252 andtwo inputs receiving signals S1OOR and S2OOR. If either or both ofsignals S1OOR or S2OOR is true, then output 252 is true—otherwise output252 is false. Output 252 provides two-state signal OOR representing thata sensor out-of-range condition or sensor power supply failure conditionhas been detected. Logic 245 also includes latching logic 254 which setsthe two-state signal LIMPHOME to true to indicate a limp-home conditionif signal OOR is true. If later an idle position of pedal 222 isdetermined and OOR is false, then logic 254 sets LIMPHOME to false.

FIG. 9 illustrates control logic 260 which may be used to verifyconformance between sensors 224 and 226. Logic 260 includes adders 262,272 and 282 each including a positive input (+), a negative input (−)and an output indicated by the departing arrow head, and logicalswitches 268 and 278. Adders 262, 272 and 282 subtract the value attheir negative input from the value at their positive input and outputthe resulting value. The positive input of adder 262 is connected tosignal S1. The negative input of adder 262 is connected to the output oflogical switch 268. Similarly, the positive input of adder 272 isconnected to signal S2, and the negative input of adder 272 is connectedto the output of logical switch 278. The output of adder 262 isconnected to the positive input of adder 282 and the output of adder 272is connected to the negative input of adder 282. Thus adder 282 outputsa value corresponding to the value output from adder 262 less the valueoutput from adder 272.

Switch 268 includes two input poles: zero input 268 a and auto-zeroinput 268 b receiving signal S1AZ. Signal S1AZ is an automatic zeroingvalue for signal S1 to account for sensor manufacturing variation anddrift that might occur, for example, due to wear or environment. Switch278 includes two input poles: zero input 278 a and auto-zero input 278 breceiving signal S2AZ. Signal S2AZ is an automatic zeroing value forsignal S2. The generation of signals S1AZ and S2AZ is further describedin connection with the logic of FIG. 11 hereinafter.

Switches 268 and 278 each includes a respective toggle input indicatedby a phantom line input arrow connected to two-state signal AZON. Whensignal AZON is true, switches 268 and 278 make contact with the pole inthe direction of the curved arrows within the switch symbols to transmitsignals S1AZ and S2AZ to the respective adders 262 and 272. In otherwords, signal AZON turns-on the autozero function providing S1AZ andS2AZ to adders 262 and 272. If AZON is false, the 0% values on inputs268 a and 278 a are transmitted through switches 268 and 278 to adders262 and 272, respectively. As a result, adders 262 and 272 pass signalsS1 and S2 through to adder 282 without auto zero adjustment.Accordingly, adder 282 outputs a difference between S1 and S2 withoutautozeroing when AZON is false, and with autozeroing when AZON is true.

Logic 260 further includes absolute value operator 280 which outputs theabsolute value or unsigned magnitude of its input, comparator 284 whichprovides a true binary output if its positive (+) input is larger thanits negative (−) input (otherwise the output is false), a logicaldebouncer 298 which generates a debounced binary signal, and latchinglogic 292. Operator 280 outputs the absolute value of the differencevalue generated by adder 282. The output of operator 280 is provided tothe positive input of comparator 284, and a DEVIATION LIMIT signal isprovided to the negative input of comparator 284. The DEVIATION LIMIT isa constant representing a threshold which, if exceeded by the differencebetween the outputs of adders 262 and 272, results in a positive outputof comparator 284. Otherwise, the output of comparator 284 is false. Inthis manner control system 260 operates to determine whether two sensoroutput values or two autozeroed sensor values are within a desired rangeof one another.

The output of comparator 284 is provided to debouncer 298. Debouncer 298delays a transition from a false to a true state by delay constantDELAY1, which could span several executions of logic 260. In otherwords, a true output of comparator 284 has to be sustained for a periodof time greater than or equal to that represented by constant DELAY1before the output of debouncer 298 changes from a false state to a truestate.

The output of debouncer 298 is provided to latching logic 292. If thisoutput is true, logic 292 sets the logical conformance failed signal CFto true. If, after a period of time, the output of debouncer 298 returnsto false, and S1 is less than or equal to S1AZ and S2 is less than orequal to S2AZ, then signal CF is reset to false. Thus, the aspects oflogic 260 described to this point permit indication of a conformancefailure relating to S1 and S2 and correspondingly sensors 224 and 226.

Logic 260 also includes a two-input logical AND operator 288 and logicalinverter 296. Inverter 296 provides its inverted output to one of theinputs of operator 288. Signal CF is provided to the other input ofoperator 288 from logic 292. Signal LIMPHOME is input to inverter 296.As a result, the output of operator 288, signal CE, is true only if CFis true and LIMPHOME is false. In this manner, logic 260 only indicatesa conformance error by making signal CE true when limp-home is notactive (LIMPHOME=true).

FIG. 10 shows control logic 300 which outputs a throttle control valuein the form of signal THROTTLE O/P and idle status of the throttle inthe form of signal TIS. When arrangement 220 is functioning properly,signal THROTTLE O/P can serve as the primary operator throttle input.Signal TIS can be utilized to determine throttle idle/nonidle status toexecute conditional 164 of subroutine 150.

Logic 300 includes inputs S1, S1AZ, S2 and S2AZ previously described inconnection with FIG. 9. Inputs S1 and S1AZ are connected to the positive(+) and negative (−) inputs of adder 306. Inputs S2 and S2AZ areconnected to the positive (+) and negative (−) inputs of adder 307.Adders 306 and 307 each output the difference provided by subtractingthe value at its negative input from the value at its positive input.

The output of adder 306 is connected to one input pole of logical switch316 and to one input of minimum value selector (MIN) 308. The output ofadder 307 is connected to one input pole of logical switch 317 and to asecond input of selector 308. Selector 308 outputs the lesser of the twoinput values that it receives. Switches 316 and 317 each also include asecond input pole of zero (0%), and a toggle control input T that causesthe respective switch output to provide the second input value of zerowhen at a logical “true” state. For switches 316 and 317, the togglesignals are provided as signals S1OOR and S2OOR, respectively, aspreviously described in connection with FIG. 8.

Logic 300 also includes logical switch 311 with one of its input polesconnected to the output of switch 316 and another input pole connectedto the output of switch 317. Switch 311 also includes a toggle controlinput T coupled to signal S1OOR that causes switch 311 to output thevalue from switch 316 when it receives a false logical input, and tooutput the value from switch 317 when it receives a true logical input.Recalling that signals S1OOR and S2OOR are true when an error conditionis determined in connection with their respective sensors 224 and 226,it should be understood switches 306, 307, and 311 cooperate to outputthe value provided by adder 306 when both signals S1OOR and S2OOR aretrue, to output the value from the sensor without the failure when onlyone of signals S1OOR and S2OOR is true, and to output the zero input ofswitch 316 when both signals S1OOR and S2OOR are true.

Logic 300 also includes logical switches 309 and 310. Selector 308provides the lesser of its two inputs to one input pole of switch 309which represents the autozeroed values of signals S1 and S2 regardlessof whether an out-of-range condition has occurred in connection witheither one. Switch 309 also includes a second input pole of zero (0%)and toggle control input T that is determined by a logical constant ZTL.Switch 309 provides its output to one input pole of switch 310 and theother input pole of switch 310 is provided the output of switch 311.Switch 310 has a toggle control input T provided from test logic 320.Test logic 320 outputs a true logic state only if signal CF produced bylogic 260 is true and signal LIMPHOME produced by logic 245 is false.Switches 309 and 310 cooperate so that the output of switch 310 comesfrom switch 311 unless there is conformance failure without a limp-homeindication. On the other hand, if CF is true and LIMPHOME is false, thenswitch 310 outputs the value provided by switch 309 as determined by theZTL constant. Accordingly, if constant ZTL is true, it causes a zerovalue to be output by switch 310 if there is a conformance failure(CF=true) and no limp-home indication (LIMPHOME=false). If ZTL is falsewith CF=true and LIMPHOME=false, then the minimum value from selector308 is output by switch 310. In this manner, constant ZTL can be used todetermine whether values from sensor 224 and/or sensor 226 causing aconformance failure without a limp-home activation are to be reliedupon.

Logic 300 also includes throttle range calculator 322, limiter 324,comparator 334, logical switches 332 and 336, and limp home active logic338. The output of switch 310 is connected to calculator 322 whichmultiplies its input by 100 and divides by a constant corresponding tothe expected throttle range to produce a normalized throttle leveloutput in terms of percentage. This output is limited to a range of 0%to 100% by limiter 324; where any input value outside this range (<0%or >100%) is output by limiter 324 as the nearest of the two rangeextremes of 0% and 100%. The limiter output is designated as signalTHROTTLE which is provided to a positive input of comparator 334 and oneof two input poles of switch 332. The negative input of comparator 334is a constant representative of a threshold idle value. If the positiveinput of comparator 334 is greater than the negative input, then itoutputs a logical true state causing the toggle input T of switch 336 tochange its output (throttle idle status signal TIS) from an idleindicating state to a nonidle indicating state. Switch 332 changes itsoutput (signal THROTTLE O/P) from signal THROTTLE to zero in response toa logical true at its toggle input T from logic 338. Logic 338 outputs alogical true state only if: (a) CF is true and LIMPHOME is false, or (b)LIMPHOME is true and neither is S1AZ below a predetermined level nor isS2 out-of-range because it is too low.

FIG. 11 shows auto-zero logic 400. Logic 400 includes logical ORoperator 401 with signals CF and LIMPHOME as inputs. If either input CFor LIMPHOME is true, a logic true state is output by operator 401 tooperators 402 and 405. In response, further autozero processing inaccordance with logic 400 is bypassed, and logic 400 is exited.Otherwise, autozero logic is processed further which is described asfollows.

Logic 400 also includes adder 416, comparator 418, debouncer 420,conditional operator 422, logic grouping 500 and logic grouping 600.Adder 416 sums a minimum throttle adjustment factor designated by signalS1 TM and a sensor confidence band constant designated by signal CB, andprovides this sum to the positive input of comparator 418. The negativeinput of comparator 418 is signal S1. Comparator 418 outputs a truelogic state if the sum of S1 TM and CB (S1 TM+CB) is greater than S1,otherwise its output is set to a logic false state. This output isdebounced with debouncer 420 using the constant DELAY2 as previouslydescribed for debouncer 298 of logic 260. The logical output ofdebouncer 420 is tested by conditional operator 422, which if true(affirmative) branches to logic grouping 500 and if false (negative)branches to logic grouping 600.

Logic grouping 500 includes adders 506, 510, and 514; and multiplier508. The throttle minimum value for S1 previously designated signal S1TM is calculated by logic grouping 500 as a function of signal S1, asensor property autozero adjustment factor designated by signal AZ A,and a previously calculated value of S1 TM, which is designated signalS1 LM. Signal S1 LM is a stored value of S1 TM from the last executionof logic group 500, or an initialization value if there were no previousexecutions. Adder 506 subtracts signal S1 LM from signal S1 and providesthe resulting difference to multiplier 508. Multiplier 508 multipliesthis difference by the adjustment factor of signal AZ A and provides theresulting product to adder 510. Adder 510 adds the product frommultiplier 508 and signal S1 LM, which sum becomes the current S1 TMsignal. Adder 514 adds signal S1 TM and an auto-zero offset constant AZOto provide the autozero signal S1AZ used with previously described logicof FIGS. 9 and 10.

Logic 400 continues with logic grouping 600 from logic grouping 500 orthe false (negative) branch of conditional operator 422. Logic grouping600 includes adder 616, comparator 618, debouncer 620, conditionaloperator 622 and logic subgrouping 700. Adder 616 sums a minimumthrottle adjustment factor for signal S2, designated signal S2 TM, andsignal CB, and provides this sum to the positive input of comparator618. The negative input of comparator 618 is signal S2. Comparator 618outputs a true logic state if the sum of S2 TM and CB (S2 TM+CB) isgreater than S2, otherwise its output is set to a logic false state.This output is debounced with debouncer 620 using the constant DELAY2 aspreviously described for debouncer 298 of logic 260. The logical outputof debouncer 620 is tested by conditional operator 622, which if true(affirmative) branches to logic subgrouping 700 and if false proceeds tooperator 405 to exit.

Logic subgrouping 700 includes adders 706, 710, and 714; and multiplier708. The throttle minimum value for S2 (signal S2 TM) is calculated bylogic subgrouping 700 as a function of signal S2, a sensor propertyautozero adjustment factor designated by signal AZ A, and a previouslycalculated value of S2 TM, which is designated signal S2 LM, in the samemanner as described for signal S1 of logic grouping 500. Signal S2 LM isa stored value of S2 TM from the last execution of logic subgrouping700, or an initialization value if there were no previous executions.Adder 706 subtracts signal S2 LM from signal S2 and provides theresulting difference to multiplier 708. Multiplier 708 multiplies thisdifference by the adjustment figure of signal AZ A and provides theresulting product to adder 710. Adder 710 adds the product frommultiplier 708 and signal S2 LM, which sum becomes current S2 TM signal.Adder 714 adds signal S2 TM and constant AZO to provide the autozerosignal S2 AZ used with previously described logic of FIGS. 9 and 10.From logic subgrouping 700, operator 405 is encountered at which pointlogic 500 is exited.

It should be understood that routine 120; subroutines 130 and 150; andcontrol logic 245, 260, 300, or 400 are each typically executed bycontroller 90 on a repetitive basis either continuously or with timeintervals lapsing between executions. Such time intervals could begenerally the same from one to the next or vary in duration.Alternatively or additionally, some or all of these routines,subroutines, and logic may be commenced, terminated and/or suspended byinterrupts. Additionally, it may be necessary to ensure a particularorder for the execution of certain routines, subroutines, and/or logicwhere one depends on another for one or more variables. Accordingly,execution may be scheduled by controller 90 in a predetermined sequencetimed as required to implement the invention. In one embodiment, certainroutines, subroutines, and logic are periodically scheduled forexecution at a frequency that is different than the periodic schedulingof other of the routines, subroutines, and logic.

As used herein, it should be appreciated that: variable, criterion,characteristic, quantity, amount, value, constant, flag, data, record,threshold, limit, input, output, matrix, command, and look-up table,each generally correspond to one or more signals within processingequipment of the present invention. It is contemplated that variousfunctional blocks, operators, operations, stages, conditionals,procedures, thresholds, and processes described in connection with thepresent invention could be altered, rearranged, substituted, deleted,duplicated, combined, or added as would occur to those skilled in theart without departing from the spirit of the present invention.

All publications, patent, and patent applications cited in thisspecification are herein incorporated by reference as if each individualpublication, patent, or patent application were specifically andindividually indicated to be incorporated by reference and set forth inits entirety herein. Any theory of operation or finding described hereinis merely intended to provide a better understanding of the presentinvention and should not be construed to limit the scope of the presentinvention as defined by the claims that follow to any stated theory orfinding. While the invention has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that only the preferred embodiment has been shown anddescribed and that all changes, modifications, and equivalents that comewithin the spirit of the invention as defined herein or by the followingclaims are desired to be protected.

1. A method, comprising: operating an internal combustion engine inresponse to a throttle signal provided with an operator-adjustedthrottle control; generating an idle status signal corresponding to anidle position of the operator-adjusted throttle control; detecting afailure of the throttle signal; and incrementally adjusting an amount offuel provided to the engine as a function of the idle status signal andthe rotational speed of the engine in response to the failure.
 2. Themethod of claim 1, which includes powering a ground traveling vehiclewith the engine and sensing brake status of the vehicle and wherein saidincrementally adjusting includes determining the amount of fuel as afunction of the brake status.
 3. The method of claim 2, wherein saidincrementally adjusting includes determining the amount of fuel as afunction of a vehicle speed value.
 4. The method of claim 1, wherein thethrottle control includes an operator adjustable pedal and a sensor toprovide the throttle signal and a switch corresponding idle position ofthe pedal to provide the idle status signal.
 5. The method of claim 1,wherein the throttle control includes an operator adjustable pedal and aset of rotary sensors to determine the throttle signal and the idlestatus signal.
 6. The method of claim 1, which includes fueling theengine after the failure in response to an operator fueling controldifferent from the throttle control.
 7. The method of claim 1, whichincludes: powering motion of the vehicle with the engine; increasingspeed of the vehicle by increasing the fuel amount provided by saidincrementally adjusting in response to a nonidle position of thethrottle control being indicated by the idle status signal; anddecreasing speed of the vehicle by reducing the fuel amount provided bysaid incrementally adjusting in response to an idle position of thethrottle control being indicated by the idle status signal.
 8. Themethod of claim 4, which includes: regulating the engine in accordancewith an engine speed governor when a vehicle speed exceeds a predefinedthreshold.
 9. A method, comprising: moving a ground traveling vehiclewith an internal combustion engine in response to a firstoperator-adjusted fueling control; detecting a failure of the firstoperator-adjusted fueling control; after the failure, adjustingoperation of the engine in response to the first operator-adjustedfueling control to limit vehicle speed; and operating the engine afterthe failure in response to a second operator-adjusted fueling control toselectively move the vehicle at a greater speed than permitted with thefirst operator-adjusted fueling control.
 10. The method of claim 9,wherein the first operator-adjusted fueling control includes a throttlecontrol arrangement with a pedal and at least one sensor to sense arange of nonidle positions of the pedal.
 11. The method of claim 9,wherein the second operator-adjusted fueling control includes a cruisecontrol for a vehicle.
 12. The method of claim 9, wherein said adjustingincludes fueling the engine after the failure in response to the firstoperator-adjusted fueling control in accordance with an idle statusindication and rotational engine speed.
 13. An apparatus, comprising: aground traveling vehicle; an internal combustion engine operable topower motion of the vehicle; a throttle control responsive to anoperator of the vehicle; a cruise control responsive to the operator ofthe vehicle; a vehicle speed sensor; and a controller responsive to thethrottle control to regulate fueling of the engine, the controller beingoperable to detect a throttle control failure and regulate engineoperation with the throttle control in an accommodation mode in responseto the failure, the controller being responsive to operator input withthe cruise control and the vehicle speed sensor to permit the engine topower the vehicle at a speed greater than with the throttle controlduring the engine operation in the accommodation mode.
 14. The apparatusof claim 13, wherein the throttle control includes an operatoradjustable pedal and means for sensing position of the pedal.
 15. Theapparatus of claim 13, wherein the throttle control includes a set ofsensors redundantly registering a range of nonidle positions of anoperator adjustable pedal.
 16. The apparatus of claim 13, wherein thecontroller includes a signal corresponding to a maximum vehicle speed inresponse to the throttle control while operating in the accommodationmode.
 17. The apparatus of claim 16, wherein the controller includesmeans for performing the accommodation mode as a function of rotationalspeed of the engine, brake status of the vehicle, and idle status of thevehicle.
 18. A method, comprising: operating a vehicle including aninternal combustion engine fueled in accordance with anoperator-adjusted throttle control; registering at least a portion of arange of multiple nonidle positions of the operator-adjusted throttlecontrol with each of two or more sensors; detecting a failure of one ofthe sensors; determining an idle status of the throttle control afterthe failure; and fueling the engine based on a limp-home mode ofoperation in accordance with the idle status and the rotational speed ofthe engine.
 19. The method of claim 18, wherein the limp-home mode ofoperation includes determining said fueling as a function of the idlestatus, rotational speed of the engine, and brake status of the vehicle.20. The method of claim 18, which includes operating the vehicle at aspeed greater than permitted by the limp-home mode of operation inresponse to activation of a cruise control by an operator.
 21. Themethod of claim 18, wherein the limp-home mode of operation includesincreasing speed of the vehicle by incrementally increasing fuelprovided to the engine during a nonidle position of the throttle controlindicated by the idle status and decreasing the speed of the vehicle byreducing the fuel for an idle position of the throttle control indicatedby the idle status.
 22. The method of claim 18, which includesregulating the engine in accordance with a speed governor when vehiclespeed exceeds a predetermined threshold.
 23. An apparatus, comprising:an internal combustion engine; a throttle control arrangement includingan operator adjustable pedal and a set of sensors to redundantly senseat least a portion of a range of multiple nonidle positions of thepedal; and a controller responsive to the set of sensors to determine aengine fueling signal corresponding to position of the pedal and an idlestatus signal representative of idle position status of the pedal, thecontroller being operable to detect a failure of the throttle controlarrangement and control the engine in a failure accommodation mode inresponse, the controller generating the engine fueling signal as afunction of the idle status signal and the rotational speed of theengine during the failure accommodation mode of operation.
 24. Theapparatus of claim 23, further comprising: a vehicle carrying theengine, the throttle control, and the controller, the engine poweringmotion of the vehicle; an operator adjustable cruise control to select adesired cruise speed of the vehicle; wherein said controller isresponsive to an operator input provided with the cruise control topermit the engine to power the vehicle at a greater speed than with thethrottle control during the control of the engine in the failureaccommodation mode.
 25. The apparatus of claim 23, further comprising avehicle carrying the engine, the throttle control, and the controller;and wherein the controller includes means for performing theaccommodation mode as a function of rotational speed of the engine andbrake status of the vehicle.
 26. An apparatus, comprising: an internalcombustion engine for powering a ground traveling vehicle; a throttlecontrol arrangement including means for sensing position of an operatoradjustable pedal to provide a throttle control signal; a first sensor tosense rotational speed of the engine; a second sensor to sense brakestatus of the vehicle; means for determining a failure of the throttlecontrol signal; and means for operating the engine in a limp-home modein response to the failure, said operating means including means forfueling the engine during the limp-home mode of operation in accordancewith idle position of the pedal, the rotational speed of the engine, andthe brake status.